George, I haven't memorized the article. You'll have to read the archived copy to discover what it does or doesn't say about the rail voltages.
You mean the 7 different diameter strands in a Fibonacci sequence (uninsultated) in each wire didn't affect your buying decision?
(Only ribbing you).
We had a customer in China that complained about "holed" parts. It took awhile to realize that they meant the die exploded and left a hole in the plastic package when they shorted the output to the rail under full output. Explaining that there was a transformer in the application and the customer could never actually short the output to the rail did not help.
Thanks Mark.
It doesn't say, that's why i asked. It only mentions the taps of the power transformer at the primary side.
Then the bulb finally lit 😀 and I looked for that transformer (Signal 56-12) on the net. It is a 2x28Vac (with 115V on the primary side).
George
It doesn't say, that's why i asked. It only mentions the taps of the power transformer at the primary side.
Then the bulb finally lit 😀 and I looked for that transformer (Signal 56-12) on the net. It is a 2x28Vac (with 115V on the primary side).
George
[US Patent 4,177,431]
I find this use of the word oscillator amusing, a sort of Freudian slip:
An interesting article that I came across by Daniel H. Cheever concieved in 2001 covering the subject of presenting a distortion figure more in line with our aural perception.
https://next-tube.com/articles/Cheever/cheever.pdf
Hans
https://next-tube.com/articles/Cheever/cheever.pdf
Hans
Hans,
Thanks for the link. Of course, it won't change anything.
Earl Geddes also tried to introduce a new distortion metric. Didn't change anything either.
Thanks for the link. Of course, it won't change anything.
Earl Geddes also tried to introduce a new distortion metric. Didn't change anything either.
It may help lab tinkerers perform "hill climbing" optimizations more quickly, to achieve Best Sound (rather than Best Measurements) for a given amplifier.
It is certainly all wrong with that paper.
Once I thought so too but then the masters of measurements explained to me that my ears don't matter because they don't prove anything, while their instruments prove the absolute truth.
How can a so poorly measuring zero feedback single ended DHT amplifier sound better than a fine measuring SS amplifier with negative feedback?
Once I thought so too but then the masters of measurements explained to me that my ears don't matter because they don't prove anything, while their instruments prove the absolute truth.
How can a so poorly measuring zero feedback single ended DHT amplifier sound better than a fine measuring SS amplifier with negative feedback?
Sorry, I can't say this thesis moves the needle for me. The literature review is unfortunately more guided storytelling of distortion measurements through the years than a critical examination of the field to highlight the strengths and weaknesses of the body of work already done. And the part about Otala's work might as well be lifting Otala's conclusions right out of the respective papers/etc rather than a more mature understanding. Furthermore I scanned the thesis looking for an actual audible testing protocol between his two amplifiers to back up the early assertions and only found anecdotal claims and reliance on selected literature. So what am I supposed to glean from this? There may be kernels of truth to what's being said, but nothing I read (and to be fair I may have missed it) makes this robust, original, literature.
Now, none of this is exactly surprising, and when I did my MS I wasn't anywhere near as attentive to methods and asking, "what was tested and how robust are the conclusions?" of papers as I am now. Funny what changes when you go from academics, "sweet it worked once, publish!" to product development will do to one's perspective. We grow with time, hopefully.
Edit: Mark, you could actually try being constructive and build a model of audibility or an honest attempt to validate prior models rather than sniping.
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Daniel,
I think what we need first is convincing evidence that at least some people, maybe only a few, can hear much more low level stuff than current mainstream models estimate. Once we have some interesting people to study, then we can consider models.
Also, I think we should study the effects of learning on hearing acuity. Seems like that could be illuminating as well.
Thus, I have thought about what it would take to make some progress in the above areas. I always get stuck when I think about the dollar cost and manpower needed to do something that would be convincing. I don't know how to do it cheap AND good.
I think what we need first is convincing evidence that at least some people, maybe only a few, can hear much more low level stuff than current mainstream models estimate. Once we have some interesting people to study, then we can consider models.
Also, I think we should study the effects of learning on hearing acuity. Seems like that could be illuminating as well.
Thus, I have thought about what it would take to make some progress in the above areas. I always get stuck when I think about the dollar cost and manpower needed to do something that would be convincing. I don't know how to do it cheap AND good.
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Not sniping. If Cheever's method does distinguish superior sounding amps then the obvious application is: use it to optimize amps for superior sound. I have done no research myself to confirm or refute the ideas he puts forward.
Even if his paper is not as solid as one would like, I think he has made a point with the SE tube amp with horrible THD figures but excellent IMD results and very positive reviews in audio magazines.
IMO reason enough to give it some thoughts.
Hans
IMO reason enough to give it some thoughts.
Hans
Mark J -- sorry didn't mean you were sniping, we have too many Marks hanging around, evidently. 🙂 I agree as far as, "if the method does work, let's use it." But as far as I read, Cheever didn't do the research himself to confirm or deny the ideas he put forward. Not to say it didn't happen elsewhere, and I hope to goodness no one goes around picking apart my theses with a fine toothed comb.
Edit to add: Hans, as a hobbyist, it's hard to argue with doing whatever is enjoyable. So if going with linear, low-loop gain designs rocks a person's boat, you don't need my approval. I just don't get excited by the paper when I put the scientist/engineer hat on. (Which is stuck on pretty hard)
Edit to add: Hans, as a hobbyist, it's hard to argue with doing whatever is enjoyable. So if going with linear, low-loop gain designs rocks a person's boat, you don't need my approval. I just don't get excited by the paper when I put the scientist/engineer hat on. (Which is stuck on pretty hard)
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Agree with Hans, the paper is not solid. However, it does come close to agreeing with what some professional high end audio designers believe. That said, those designers don't necessarily aim for particular harmonic ratios (although some do). Some others aim for a perceptual experience that they are experienced at assessing and being successful with. IMHO, there is probably more too it than Cheever's model suggests.
If you believe the audio rag reviews are you buying cable lifters and noise harvesters? Personaly I dont believe a word.